Significance and Impact of the study: Clonostachys rosea is one of the most promising biocontrol agents in countering many plant fungal diseases. However, large-scale production and commercialization are hampered by the lack of understanding of the impacts of culture conditions on performance and types of C. rosea sporulation and subsequently inadequate research on the techniques for chlamydospore production. In addressing these concerns, this study provides a unique insight into the manipulation of C. rosea sporulation and chlamydospore fermentation of the biocontrol fungus. AbstractThe promising biocontrol isolate Clonostachys rosea 67-1 was investigated to clarify the effects of culture conditions on chlamydospore production in submerged fermentation. Culture conditions significantly affected both performance and types of C. rosea sporulation. C. rosea 67-1 was hard to generate chlamydospores under conventional conditions. However, the proportion of resistant spores increased to 17Á4 and 15Á5% in PD and rice meal media, respectively, in 8 days. Chlamydospore productivity was boosted (>threefold) with the addition of 50-200 mg l À1 CuSO 4 . The pH of the medium played a vital role in 67-1 sporulation. The percentage of chlamydospores decreased rapidly with increased pH (88Á1% at pH 3Á0 to 1Á0% at pH 6Á5). The optimal pH for conidia production was 6Á0-6Á5, at which chlamydospore forming was strongly inhibited. Regulating pH during fermentation contributed to improving output and proportion of resistant spores. When 67-1 was inoculated into broth with an initial pH of 6Á5, followed by adjustment to pH 3Á5 after 48 h, the number of chlamydospores reached 1Á1 9 10 8 ml À1 . The impact of temperature and rotational speed was also analysed; an ultimate capacity of chlamydospores was achieved at 30°C and the speed above 120 rev min À1 (P < 0Á05).

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